Method and apparatus for controlling access to a multimedia broadcast multicast service in a packet data communication system

ABSTRACT

A communication system ( 100 ) determines whether to establish a point-to-multipoint communication or a point-to-point communication for conveyance of Multimedia Broadcast Multicast Service (MBMS) data based on a number of mobile stations (MSs) ( 102 - 104 ), both idle mode and maintaining an active connection, serviced by the system and subscribed to an MBMS service. The system, broadcasts ( 306 ) a control message that includes an access probability factor. In order to avoid overloading the system with responses to the control message, MSs maintaining an active connection ignore ( 506, 508 ) the control message while idle mode MSs determine ( 506, 512 ) whether to respond based on the access probability factor. The system compares ( 310 ) a number of received responses to a threshold and determines whether to establish a point-to-multipoint communication ( 312 ) or a point-to-point communication ( 322 ) based on the comparison. The system also adjusts ( 314, 330 ) the access probability factor based on the number of responses.

FIELD OF THE INVENTION

The present invention relates generally to packet data communicationsystems, and, in particular, to a multimedia broadcast multicast servicein a packet data communication system.

BACKGROUND OF THE INVENTION

The Universal Mobile Telecommunication Service (UMTS) standard providesa compatibility standard for cellular mobile telecommunications systems.The UMTS standard ensures that a mobile station (MS), or a userequipment (UE), operating in a UMTS system can obtain communicationservices when operating in a system manufactured according to thestandard. To ensure compatibility, radio system parameters and datatransfer procedures are specified by the standard, including protocolsgoverning digital control messages and bearer traffic that are exchangedover an air interface.

The UMTS standards provide, in 3GPP TS 25.346 (Third GenerationPartnership Project Technical Specification 25.346) v0.5.0 and 3GPP TS23.846 v6.0.0, for a provision of a Multimedia Broadcast MulticastService (MBMS) service by a UMTS communication system to UEs serviced bythe system. The MBMS service provides for a multicast and unicast ofMBMS data, typically in a format of Internet Protocol (IP) data packetsto one or more of the UEs. In order to ensure that the air interfaceresources of the UMTS communication) system are not wasted, the systemmust first estimate the number of recipients, that is subscribed UEs, ina cell providing MBMS deals. Based on the estimated number ofrecipients, the system then determines whether to establish aPoint-To-Multipoint (PTM) communication channel in the cell or aPoint-To-Point (PTP) channel to each recipient. When the estimatednumber of recipients in the cell exceeds an operator defined threshold,the system establishes a PTM channel in the cell. When the estimatednumber of recipients in the cell is less than the operator definedthreshold, the system establishes a PTP channel to each subscribing MSin the cell.

Typically, the system estimates the number of recipients based on anumber of UEs subscribing to MBMS services that are active overestablished connections. Based on the estimate, a Radio NetworkController (RNC) included in a UMTS infrastructure determines whether toestablish a PTM communication channel in the cell or a PTP communicationchannel to each UE. The RNC then broadcasts a MBMS notification via aNode B, typically a base transceiver station (BTS), and a controlchannel to all UEs in the cell. The notification typically includes anidentifier associated with the MBMS service. In response to receivingthe MBMS notification, each UE in the cell that subscribes to the MBMSservice may then convey a connection request, typically a Radio ResourceControl (RRC) connection establishment request, to the RNC via an accesschannel. Upon receiving the connection requests from each of thesubscribing UEs, the RNC establishes a PTM communication channel orestablishes PTP communication channels with each responding UE,whichever the RNC has determined to establish, and conveys the MBMS datato the subscribing UEs over the established channel or channels.

In order to limit the number of connection requests generated inresponse to the MBMS notification, it has been proposed to broadcast anaccess probability factor in conjunction with the MBMS notification.However, a problem arises in that, typically, the RNC is not aware of anumber of idle mode UEs in a cell that have subscribed to an MBMSservice. Since the idle mode UEs do not have active connections with theRNC, the RNC does not count these UEs when estimating a number ofrecipients of the MBMS data. When the access probability factor is setto a high value and the number of idle mode UEs subscribing to the MBMSservice is also large, an access channel can be overloaded by the numberof connection requests generated in response to the MBMS notification.In the event of a system overload, the UMTS standards permit an operatorof the system to employ a back-off mechanism. However, back-offmechanisms produce connection set-up delays and waste RF resources asUEs must repeatedly transmit connection requests. On the other hand,when the access probability factor is set to a low value and the numberof idle mode MSs subscribing to the MBMS service is small, the number ofconnection requests received by the RNC in response to a countingrequest may be insufficient to invoke establishment of a PTM channelwhen a PTM channel may be the most efficient scheme for disseminatingthe multimedia data.

Therefore, a need exists for a method and apparatus that provides a moreaccurate estimate of a number of mobile stations serviced by a systemand subscribed to MBMS service, including idle mode mobile stations,while limiting a number of connection requests generated in response toan MBMS notification, and that provides for dynamic adjustment of anaccess probability factor that controls the number of connectionrequests.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication system inaccordance with an embodiment of the present invention.

FIG. 2 is a block diagram of a mobile station of FIG. 1 in accordancewith an embodiment of the present invention.

FIG. 3A is a logic flow diagram depicting a method for determiningwhether to establish a Point-To-Multipoint (PTM) communication or aPoint-to-Point (PTP) communication for conveyance of MultimediaBroadcast Multicast Service (MBMS) data to subscribing mobile stationsin accordance with an embodiment of the present invention.

FIG. 3B is a continuation of the logic flow diagram of FIG. 3A depictinga method for determining whether to establish a PTM communication or aPTP communication for conveyance of MBMS data to subscribing mobilestations in accordance with an embodiment of the present invention.

FIG. 4 is a logic flow diagram depicting a method for determiningwhether to to subscribing mobile stations in accordance with anotherembodiment of the present invention.

FIG. 5 is a logic flow diagram of steps executed by a mobile station ofFIG. 1 in responding to a control message in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

To address the need for a method and an apparatus that that provides amore accurate estimate of a number of mobile stations serviced by asystem and subscribed to MBMS service, including idle mode mobilestations, while limiting a number of connection requests generated inresponse to an MBMS notification, and that provides for dynamicadjustment of an access probability factor that controls the number ofconnection requests, a communication system determines whether toestablish a point-to-multipoint communication or a point-to-pointcommunication for conveyance of Multimedia Broadcast Multicast Service(MBMS) data based on a number of mobile stations, both idle mode andmaintaining an active connection, serviced by the system and subscribedto an MBMS service. The system broadcasts a control message thatincludes an access probability factor. In order to avoid overloading thesystem with a number of responses generated in response to the controlmessage, mobile stations maintaining an active connection ignore thecontrol message while idle mode mobile stations determine whether torespond based on the access probability factor. The system compares anumber of responses received in response to the control message to athreshold and determines whether to establish a point-to-multipointcommunication or a point-to-point communication based on the comparison.The system also adjusts the access probability factor based on thenumber of responses.

Generally, an embodiment of the present invention encompasses a methodfor controlling access to a Multimedia Broadcast Multicast Service(MBMS) service. The method includes determining a quantity of mobilestations subscribed to the MBMS service and maintaining an activeconnection, determining an access probability factor, and broadcasting acontrol message comprising the access probability factor. The methodfurther includes receiving, from each of one or more idle mode mobilestations, a response to the control message, comparing the number ofreceived responses to a threshold to produce a comparison, anddetermining whether to establish a point-to-multipoint communication ora point-to-point communication based on the comparison.

Another embodiment of the present invention encompasses a method foraccessing a Multimedia Broadcast Multicast Service (MBMS) service. Themethod includes receiving, by a mobile station, a control messageassociated with the MBMS service and comprising an access probabilityfactor. The method further includes ignoring the control message when anactive connection exists between the mobile station and aninfrastructure and, when an active connection does not exist between themobile station and an infrastructure, determining whether to respond tothe control message based on the access probability factor.

Yet another embodiment of the present invention encompasses an apparatusfor controlling access to a Multimedia Broadcast Multicast Service(MBMS) service. The apparatus includes at least one memory device thatmaintains an access probability factor and further maintains a record ofa quantity of mobile stations subscribed to the MBMS service andmaintaining an active connection. The apparatus further includes aprocessor coupled to the at least one memory device that determines aquantity of mobile stations subscribed to the MBMS service andmaintaining an active connection and an access probability factor byreference to the at least one memory device, conveys a control messagecomprising the access probability factor, receives, from each of one ormore idle mode mobile stations, a response to the control message;compares the number of received responses to a threshold to produce acomparison, and determines whether to establish a point-to-multipointcommunication or a point-to-point communication based on the comparison.

Still another embodiment of the present invention encompasses a mobilestation capable of accessing a Multimedia Broadcast Multicast Service(MBMS) service. The mobile station includes a receiver that receives acontrol message associated with the MBMS service and comprising andaccess probability factor. The mobile station further includes aprocessor operably coupled to the receiver that receives the controlmessage from the receiver, ignores the control message when an activeconnection exists between the mobile station and an infrastructure, and,when an active connection does not exist between the mobile station andan infrastructure, determines whether to respond to the control messagebased on the access probability factor.

The present invention may be more fully described with reference toFIGS. 1-5. FIG. 1 is a block diagram of a wireless communication system100 in accordance with an embodiment of the present invention.Communication system 100 includes multiple mobile stations (MSs), oruser equipment, 102-104 (three shown) in wireless communication with aRadio Access Network (RAN) 110. RAN 110 includes at least onetransceiver, or Node B, 112 that is operably coupled to a controller114, preferably a Radio Network Controller (RNC). Communication system100 further includes a support node 120 coupled to RAN 110. Support node120 typically includes one or more Serving 3G-GPRS Support Nodes (SGSNs)that are each coupled to one or more 3G-Gateway GPRS Support Nodes(GGSNs). However, the precise architecture of support node 120 is tip toan operator of communication system 100 and is not critical to thepresent invention. Together, RAN 110 and support node 120 arecollectively referred to herein as an infrastructure 122.

Each of MSs 102-104 subscribes to a Multimedia Broadcast MulticastService (MBMS) service provided by communication system 100, whichservice provides for a distribution of MBMS data to the MSs. MBMSservices are described in detail in the 3GPP (Third GenerationPartnership Project) standards, and in particular 3GPP TS (TechnicalSpecification) 25.346 v0.5.0, 3GPP TS 23.846 v6.0.0, 3GPP TS 22.146v6.0.0, 3GPP TR (Technical Report) 21.905 v5.4.0, and Report R2-030063,which specifications and reports are hereby incorporated by referenceherein and copies of which may be obtained from the 3GPP via theInternet or from the 3GPP Organization Partners' Publications Offices atMobile Competence Centre 650, route des Lucioles, 06921 Sophia-AntipolisCedex, France.

RAN 110 provides communications services to mobile stations, such a MS102-104, located in a coverage area, such as a cell, serviced by the RANvia in air interface 128. Air interface 128 comprises a downlink 130 andan uplink 135 that each includes multiple communication channels.Preferably, downlink 130 includes a paging channel 131, at least onedownlink control channel 132, and at least one downlink traffic channel133. Preferably, uplink link 135 includes an uplink access channel 136,at least one uplink signaling channel 137, and at least one uplinktraffic channel 138.

Referring now to FIGS. 1 and 2, controller 114 and each of MSs 102-104includes a respective processor 116, 206 such as one or moremicroprocessors, microcontrollers, digital signal processors (DSPs),combinations thereof or such other devices known to those havingordinary skill in the art. Controller 114 and each of MSs 102-104further includes a respective one or more memory devices 118, 208associated with the respective processor, such as random access memory(RAM), dynamic random access memory (DRAM), and/or read only memory(ROM) or equivalents thereof, that store data and programs that may beexecuted by the processor and allow the processor to operate incommunication system 100. The one or more memory devices 118 ofcontroller 114 further maintains information concerning all MSs that areserviced by the controller and that currently maintain an activeconnection with RAN 110. Each of MSs 102-104 further includes a receiver202 and a transmitter 204 that are operably coupled to processor 206 andthat respectively provide for receiving and transmitting messages by theMS.

Preferably, communication system 100 is a Universal MobileTelecommunication Service (UMTS) communication system that operates inaccordance with the 3GPP (Third Generation Partnership Project)standards, which provide a compatibility standard for UMTS airinterfaces and which standards are hereby incorporated herein in theirentirety. The standards specify wireless telecommunications systemoperating protocols, including radio system parameters and callprocessing procedures. In communication system 100, the communicationchannels of forward link 130 or reverse link 135, such as accesschannels, control channels, paging channels, and traffic channels, eachcomprises one or more of multiple time slots in a same frequencybandwidth. However, those who are of ordinary skill in the art realizethat communication system 100 may operate in accordance with anywireless telecommunication system, such as but not limited to a GeneralPacket Radio Service (GPRS) communication system, a Code DivisionMultiple Access (CDMA) 2000 communication system, or an OrthogonalFrequency Division Multiple Access (OFDM) communication system.

Communication system 100 further includes a Multimedia BroadcastMulticast Service (MBMS) data source 126, such as an Internet Protocol(IP) multicast server, that is coupled to infrastructure 122, and inparticular to support node 120, via a data network 124, such as an IPnetwork. As part of the MBMS service subscribed to by each of MSs102-104, MBMS data source 126 sources MBMS data, typically in the formof IP data packets, to MSs 102-104 via support node 120 and RAN 110, andin particular via controllers servicing the service subscribers, thatis, controller 114 with respect to MSs 102-104. When RAN 110, and inparticular controller 114, receives the MBMS data, the RAN must thendetermine whether to convey the MBMS data to each of the subscribing MSsserviced by the RAN, that is MSs 102-304, via a multicast, orPoint-To-Multipoint (PTM), communication channel or individual unicast,or Point-To-Point (PTP), communication channels.

In order to determine whether to establish a PTM communication channelor individual PTP communication channels, RAN 110 must first estimatethe number of MSs located in the coverage area serviced by the RAN andsubscribing to the MBMS service sourcing the MBMS data and determine anaccess probability factor based on the estimate. In prior art proposals,a RAN determines an access probability factor based on a number of MSswith active connections to the RAN and subscribing to the MBMS service.However, such a determination fails to account for idle mode MSsserviced by the RAN and subscribing to the MBMS service. As a result, inthe prior art, when a large number of idle MSs subscribe to the serviceand the access probability factor is set to a high value, the determinedan access probability factor could result in an overloading of an accesschannel by a number of MSs responding to an MBMS notification or, when asmall number of idle MSs subscribed to the service and the RAN set anaccess probability factor to a low value, the number of connectionrequests received by the RNC in response to a counting request may beinsufficient to invoke establishment of a PTM channel when a PTM channelmay be the most efficient scheme for disseminating the multimedia data.

In order to prevent all uplink access channel 136 from being,overwhelmed by connection requests in response to an MBMS notification,and to provide for an appropriate selection of a PTM connection orindividual PTP connections for conveyance of MBMS data, communicationsystem 100 provides for a more accurate method of estimating a number ofMSs subscribing to an MBMS service and located in a service area of RAN110 while limiting a number of MSs responding to the MBMS notification,and further provides an adoptively determined access probability factorto optimize the number of responses and the estimate of the number ofsubscribing MSs. FIGS. 3A and 3B depict a logic flow diagram 300 of amethod executed by communication system 100 in estimating a number ofMSs subscribing to an MBMS service and determining whether to establisha PTM communication a PTP communication for conveyance of MBMS data inaccordance with an embodiment of the present invention. Logic flowdiagram 300 begins (301) when RAN 110, and in particular controller 114,determines (302) a quantity of MSs subscribed to the MBMS service andmaintaining an active connection with the RAN. Preferably processor 116of controller 114 determines the quantity of MSs maintaining an activeconnection with the RAN by reference to memory 118. Unless otherwisespecified herein, all functions performed herein by RAN 110 areperformed by controller 114, and specifically by processor 116 ofcontroller 114. Furthermore, unless otherwise specified herein, allfunctions performed herein by controller 114 are performed by processor116 of controller 114.

RAN 110, specifically controller 114, initializes (304) an accessprobability factor ‘P,’ that is, sets ‘P’ equal to an initial accessprobability factor, ‘P_(init),’ that is maintained in memory 118 ordetermined based on an algorithm) maintained in memory 118 of controller114. RAN 110 then broadcasts (306), via transceiver 112 and downlinkcontrol channel 132, preferably an MBMS control channel, one or morecontrol messages that includes the initialized access probability factor‘P.’ The one or more control messages further includes information thatallows each MS 102-104 to determine that the MS is an intended recipientof the message, such as an identifier associated with the MBMS service,an identifier associated with an MBMS service group of which each MS102-104 is a member, or an identifier uniquely associated with each MS102-104 that is a member of the MBMS service group and/or subscribes tothe MBMS service. Preferably, the one or more control messages comprisea modified version of an MBMS notification message that is defined in3GPP TS 23.846 v6.0.0, which notification message is modified to includethe access probability factor.

In response to broadcasting the one or more control messages thatincludes the access probability factor ‘P,’ RAN 110 receives (308) aquantity of responses ‘N,’ preferably requests to establish aconnection, via uplink access channel 136. The responses are conveyed toRAN 10 only by idle mode MSs subscribed to the MBMS service, as each MSsubscribed to the MBMS service and maintaining an active connection tothe RAN ignores, that is, does not respond to, the one or more controlmessages. Preferably, each request to establish a connection comprises aconnection request, such as a Radio Resource Control (RRC) connectionestablishment request, and corresponds to an MS, such as MSs 102-104,subscribing the MBMS service and desirous of establishing a connectionand receiving the MBMS data. Since communication system 100 adaptivelydetermines the access probability factor ‘P,’ the initial accessprobability factor ‘P_(init)’ can be set small enough to ensure thatresponses to the broadcast control message do not overload accesschannel 136.

For example, in one embodiment of the present invention, the initialaccess probability factor ‘P_(init)’ may be determined by RAN 110 bysolving the following equation for P_(init), which equation may bemaintained in memory 118 of controller 114:

${\sum\limits_{i = 0}^{M}\;{C_{L}^{i}{P_{init}^{i}\left( {1 - P_{init}} \right)}^{L - i}}} \leq {1 - {p.}}$The factor ‘M’ corresponds to an adjusted multicast threshold, that is,to a multicast threshold that is reduced by the quantity of MSssubscribed to the MBMS service and maintaining an active connection withthe RAN. The multicast threshold may be predetermined by the operator ofsystem 100 and may be maintained in memory 118 of controller 114 andcorresponds to a quantity of responding MSs below which the RAN willestablish individual PTP communication channels and above which the RANwill establish a PTM communication channel to distribute the MBMS data.Preferably, the multicast threshold is a fixed value that may bedetermined based on system simulations or past experience. Controller114 then determines the adjusted multicast threshold ‘M’ by reference tomemory 118 and based on the determined quantity of MSs subscribed to theMBMS service and maintaining an active connection with the RAN. Thefactor ‘p’ corresponds to single-broadcast success probability, that is,a probability that only a single iteration will be needed to estimatethe number of MSs subscribing to the MBMS service and serviced by RAN110. The factor ‘C^(i) _(L)’ corresponds to a combination factor andrefers to selecting ‘i’ objects from a set comprising ‘L’ objects. Forexample, ‘C³ ₁₀’ may correspond to selecting 3 users from a set of 10users. The parameter ‘L’ corresponds to a target maximum number of idlemode MSs. For example, if one desired to make a single broadcast of theaccess probability factor successful, and the probability is greaterthan 0.95 (95 percent) that the number of idle mode MSs is less than200, and 0.95 is an acceptable probability, then L may be set equal to200.

RAN 110 then compares (310) the quantity of responses ‘N’ to theadjusted multicast threshold ‘M’ to produce a comparison and, based onthe comparison, determines whether to establish a PTP communication or aPTM communication for conveyance of the MBMS data. When RAN 110determines (310) that ‘N’ is greater than ‘M,’ the RAN establishes (312)a PTM communication channel in accordance with well known techniques andadjusts (314) the initial access probability factor ‘P_(init)’ based onthe quantity of responses ‘N’ and the adjusted multicast threshold ‘M.’Preferably, RAN 110 sets the initial access probability factor‘P_(init)’ equal to P*M/N, that is, sets P_(init)=P*M/N. By adjustingthe access probability factor based on the number of responses receivedin response to the broadcast of the control message, RAN 110 implementsan access probability factor that is low enough that it limits thequantity of responses to a number that will not overload the accesschannel and is high enough that the quantity of responses will properlyinvoke a PTM communication or a PTP communication for conveyance of theMBMS data. RAN 110 then conveys (316) the MBMS data to subscribing MSs102-104 via transceiver 112 and the established PTM communicationchannel. The logic flow then ends (318).

When RAN 110 determines (3110) that the quantity of responses ‘N’ isless than or equal to the adjusted multicast threshold ‘M,’ the RANfurther determines whether to establish a PTP communication or a PTMcommunication for conveyance of the MBMS data based on the accessprobability factor. RAN 110 determines (320) whether the accessprobability factor ‘P’ is equal to one (1), that is, whether P=1. WhenRAN 110 determines that ‘P’ is equal to one (1), the RAN establishes(322) a PTP communication channel in accordance with well knowntechniques with each MS 102-104 responding to the control message andconveys (324), via transceiver 112 and the established PTP communicationchannels, the MBMS (data to each of the MSs. The logic flow then ends(318).

When RAN 110 determines that the access probability factor ‘P’ is notequal to one (1), the RAN further determines whether to establish a PTPcommunication or a PTM communication for conveyance of the MBMS databased on the received quantity of responses ‘N.’ Preferably, RAN 110determines whether to establish a PTP communication or a PTMcommunication by determining (326) whether the quantity of responses ‘N’is equal to zero (0), that is, whether N=0. When RAN 110 determines(326) that the quantity of responses ‘N’ is equal to zero (0), then theRAN sets (328) the access probability factor ‘P’ equal to one (1) andestablishes (322) a PTP communication channel in accordance with wellknown techniques with each MS 102-104 responding to the control message.RAN 110 then conveys (324), via transceiver 112 and the established PTPcommunication channels, lie MBMS data to each of the MSs. The logic flowthen ends (318).

When RAN 110 determines (326) that the quantity of responses ‘N’ is notequal to zero (0), then the RAN adjusts (330) the access probabilityfactor ‘P’ based on the quantity of responses ‘N’ and the adjustedmulticast threshold ‘M.’ Preferably, RAN 110 adjusts the accessprobability factor ‘P’ by setting ‘P’ equal P*M/N, that is, settingP=P*M/N. RAN 110 then compares (332) the adjusted access probabilityfactor ‘P’ to an access probability factor threshold ‘P_(T)’ maintainedin memory 118 and determines (334) based on the comparison, whether theadjusted access probability factor is greater than the accessprobability factor threshold. When the adjusted access probabilityfactor ‘P’ is less than or equal to the access probability factorthreshold ‘P_(T),’ no further adjustment is made to the adjusted accessprobability factor ‘P’ and logic flow diagram proceeds to step 338. Whenthe adjusted access probability factor ‘P’ is greater than the accessprobability factor threshold ‘P_(T),’ RAN 110 readjusts (336) the accessprobability factor ‘P,’ that is, sets the access probability factor ‘P’equal to one (1). RAN 110 then determines (338) whether the (re)adjustedaccess probability factor ‘P’ is greater than one (1).

If RAN 110 determines that the (re)adjusted access probability factor‘P’ is less than or equal to one (1), logic flow diagram 300 returns tostep 306 and the RAN broadcasts a control message that includes the(re)adjusted access probability factor ‘P’ and further includes anidentifier associated with the MBMS service via transceiver 112 anddownlink control channel 132. In response to broadcasting the one ormore control messages that includes the (re)adjusted access probabilityfactor ‘P,’ RAN 110 receives (308) another quantity of responses,preferably requests to establish a connection, via uplink access channel136. Again, the responses are conveyed to RAN 110 only by idle mode MSssubscribed to the MBMS service, as each MS subscribed to the MBMSservice and maintaining an active connection to the RAN does not respondto the broadcast control message. RAN 110 then compares (310) theanother quantity of responses to the adjusted multicast threshold ‘M’ toproduce another comparison and determines, based on the anothercomparison and as is described above in steps 312 through 338, whetherto establish a PTP communication or a PTM communication for conveyanceof the MBMS data

If RAN 110 determines that the (re)adjusted access probability factor‘P’ is greater than one (1), the logic flow proceeds to step 322,wherein RAN 110 establishes a PTP communication channel in accordancewith well known techniques with each MS 102-104 responding to thecontrol message. RAN 110 then conveys (324), via transceiver 112 and theestablished FTP communication channels, the MBMS data to each of MSs102-104. The logic flow then ends (318).

In another embodiment of the present invention, a simplified approach isprovided to the determination of whether to establish a PTMcommunication a PTP communication based on a number of idle mode mobilestations responding to a control message. FIG. 4 depicts a logic flowdiagram 400 of a method executed by communication system 100 inestimating a number of MSs subscribing to an MBMS service anddetermining whether to establish a PTM communication channel or multiplePTP communication channels in accordance with another embodiment of thepresent invention. Similar to logic flow diagram 300, logic flow diagram400 begins (401) when RAN 110, and in particular controller 114,determines (402) a quantity of MSs subscribed to the MBMS service andmaintaining an active connection with the RAN. Preferably processor 116of controller 114 determines the quantity of MSs maintaining an activeconnection with the RAN by reference to memory 118.

RAN 110, specifically controller 114, initializes (404) an accessprobability factor ‘P,’ that is, sets ‘P’ equal to an initial accessprobability factor, ‘P_(init),’ that is maintained in memory 118 ofcontroller 114. RAN 110 then broadcasts (406), via transceiver 112 anddownlink control channel 132, preferably an MBMS control channel, one ormore control messages that includes the initialized access probabilityfactor ‘P’ and that further includes information that allows each MS102-104 to determine that the MS is an intended recipient of themessage. Similar to logic flow diagram 300, the one or more controlmessages preferably comprise a modified version of an MBMS notificationmessage that is defined in 3GPP TS 23.846 v6.0.0, which notificationmessage is modified to include the initialized access probabilityfactor.

In response to broadcasting the one or more control messages thatincludes the initialized access probability factor ‘P,’ RAN 110 receives(408) a quantity of responses ‘N,’ preferably requests to establish aconnection, via uplink access channel 136. The responses are conveyed toRAN 110 only by idle mode MSs subscribed to the MBMS service.Preferably, each request to establish a connection comprises aconnection request, such as a Radio Resource Control (RRC) connectionestablishment request, and corresponds to an MS, such as MSs 102-104,subscribing the MBMS service and desirous of establishing a connectionand receiving the MBMS data.

RAN 110 then determines (410) whether the quantity of responses ‘N’ isgreater than or equal to the adjusted multicast threshold ‘M.’ When RAN10 determines that ‘N’ is greater than or equal to ‘M,’ the RANestablishes (412) a PTM communication channel in accordance with wellknown techniques and adjusts (414) the initial access probability factor‘P_(init)’ based on the quantity of responses ‘N’ and the adjustedmulticast threshold ‘M.’ Preferably, RAN 110 sets the initial accessprobability factor ‘P_(init),’ equal to P*M/N, that is, setsP_(init)=P*M/N. RAN 110 then conveys (416), via transceiver 112 and theestablished PTM communication channel, the MBMS data. The logic flowthen ends (418).

When RAN 110 determines that the quantity of responses ‘N’ is less thanthe adjusted multicast threshold ‘M,’ the RAN adjusts (420) the accessprobability factor ‘P’ based on the quantity of responses ‘N’ and theadjusted multicast threshold ‘M.’ Preferably, RAN 110 sets the accessprobability factor ‘P’ equal to P*M/N, that is, sets P=P*M/N. RAN 110then determines (422) whether the adjusted access probability factor ‘P’is greater than or equal to one (1), that is, whether P≧1. When RAN 110determines that ‘P’ is greater than or equal to one (1), the RANestablishes (424) a PTP communication channel in accordance with wellknown techniques with each MS 102-104 responding to the control messageand conveys (426), via transceiver 112 and the established PTPcommunication channels, MBMS data to each of the MSs. The logic flowthen ends (418). When RAN 110 determines that ‘P’ is less than one (1),logic flow diagram 400 returns to step 406, where the RAN broadcasts,via transceiver 112 and downlink control channel 132, preferably an MBMScontrol channel, one or more control messages that includes the adjustedaccess probability factor ‘P’ and that further includes information thatallows each MS 102-104 to determine that the MS is an intended recipientof the message. Communication system 100 then repeats whichever stepsare appropriate of steps 408 through 426.

FIG. 5 is a logic flow diagram 500 of steps executed by each of MSs102-104 in responding to a control message received from RAN 110 inaccordance with an embodiment of the present invention. Unless otherwisespecified, all functions performed herein by each of MSs 102-104 areperformed by processor 206 of the MS. Logic flow diagram 500 begins(502) when an MS, such as MSs 102-104, serviced by RAN 110 receives(504) a control message from the RAN identifying an MBMS service towhich the MS subscribes. In response to receiving lie control message,the MS determines (506) whether the MS a connection, preferably aResource Control (RRC) connection, is established between the MS and RAN110. When the MS determines that a connection is established, the MSignores (508), that is, does not respond to, the control message and thelogic flow ends (510).

When the MS determines that a connection is not established, forexample, when the MS is in an idle mode, the MS determines (512) whetherto respond to the control message based on the access probability factor‘P’ included in the control message.

Preferably, the step of determining whether to respond comprises thefollowing steps. The MS performs a uniform random draw test over theinterval [0,1] that produces probability factor ‘P_(rand).’ Uniformrandom draws tests are well known in the art and will not be describedin greater detail. The MS then compares the probability factor producedby the uniform random draw test, that is, ‘P_(rand),’ to the accessprobability factor ‘P’ included in the control message. When theprobability factor ‘P_(rand)’ is greater than or equal to the accessprobability factor ‘P,’ the MS determines not to respond to the controlmessage, that is, ignores (514) the control message, and the logic flowends (510). When the probability factor ‘P_(rand)’ is greater than orequal to the access probability factor ‘P,’ the MS determines toestablish a connection, preferably an RRC connection, with RAN 110 andconveys (516) a request for a connection, preferably an RRC connectionestablishment request, to the RAN via uplink access channel 136. Thelogic flow then ends (510).

In summarization, communication system 100 determines whether toestablish a PTM communication or a PTP communication for conveyance ofMultimedia Broadcast Multicast Service (MBMS) data based on a number ofMSs (102-104), both idle mode and maintaining an active connection,serviced by the system and subscribed to an MBMS service. Communicationsystem 100 broadcasts a control message that includes an accessprobability factor. In order to avoid overloading the system with anumber of responses generated in response to the control message, MSsmaintaining an active connection ignore the control message while idlemode mobile stations determine whether to respond based on the accessprobability factor. Communication system 100 compares a number ofresponses received in response to the control message to a threshold anddetermines, based on the comparison, whether to establish a PTMcommunication or a PTP communication for conveyance of the MBMS data.When the comparison indicates that the number of responses does notexceed the threshold, communication system 100 may further consider oneor more of the access probability factor and the quantity of responsesreceived in determining whether to establish a PTM communication or aPTP communication. The system also adjusts the access probability factorbased on the number of received responses in order to control a quantityof responses generated by any subsequent broadcasts of the controlmessage.

While the present invention has been particularly shown and describedwith reference to particular embodiments thereof, it will be understoodby those skilled in the art that various changes may be made andequivalents substituted for elements thereof without departing from thescope of the invention as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather then a restrictive sense, and all such changes and substitutionsare intended to be included within the scope of the present invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims. As used herein, the terms“comprises,” “comprising,” or any variation thereof, are intended tocover a non-exclusive inclusion, such that a process, method, article,or apparatus that comprises a list of elements does not include onlythose elements but may include other elements not expressly listed orinherent to such process, method, article, or apparatus. It is furtherunderstood that the use of relational terms, if any, such as first andsecond, top and bottom, and the like are used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions.

1. A method for controlling access to a Multimedia Broadcast MulticastService (MBMS) service comprising: determining a quantity of mobilestations (MSs) subscribed to the MBMS service and maintaining an activeconnection; determining an access probability factor; broadcasting acontrol message comprising the access probability factor; receiving,from each of one or more idle mode mobile stations, a response to thecontrol message; comparing the number of received responses to athreshold to produce a comparison; and determining whether to establisha point-to-multipoint communication or a point-to-point communicationbased on the comparison, wherein it is determined to establish apoint-to-multipoint communication when the number of responses exceedsthe threshold; and upon determining to establish a point-to-multipointcommunication: adjusting the access probability factor based on thenumber of responses from idle mode mobile stations and the threshold,and establishing a point-to-multipoint communication channel.
 2. Themethod of claim 1, wherein the threshold comprises a threshold adjustedby the determined quantity of mobile stations subscribed to theMultimedia Broadcast Multicast Service (MBMS) service and maintaining anactive connection.
 3. The method of claim 1, wherein determining whetherto establish a point-to-multipoint (PTM) communication or apoint-to-point (PTP) communication comprises, when the number ofreceived responses does not exceed the threshold, determining whether toestablish a PTM communication or a PTP communication based on the accessprobability factor.
 4. The method of claim 3, wherein determiningwhether to establish a point-to-multipoint (PTM) communication or apoint-to-point (PTP) communication comprises: when the number ofreceived responses docs not exceed the threshold, determining whetherthe access probability factor is equal to one (1); when the accessprobability factor is not equal to one (1), determining whether toestablish a PTM communication or a PTP communication based on the numberof idle mode mobile stations responding to the control message.
 5. Themethod of claim 1, wherein determining to establish a point-to-point(PTP) communication comprises: determining whether the accessprobability factor is equal to one (1); when the number of receivedresponses does not exceed the threshold and when the access probabilityfactor is equal to one (a), establishing a PTP communication channelwith each MS responding to the control message.
 6. The method of claim1, wherein determining to establish a point-to-point (PTP) communicationcomprises: determining whether the access probability factor is equal toone (1); when the access probability factor is not equal to one (1),determining whether the number of idle mode mobile stations respondingto the control message is equal to zero (0); and when the number ofreceived responses does not exceed the threshold and when the number ofidle mode mobile stations responding to the control message is equal tozero (0), establishing a PTP communication channel with each MSresponding to the control message.
 7. The method of claim 1, whereindetermining whether to establish a point-to-multipoint (PTM)communication or a point-to-point (PTP) communication when the number ofreceived responses does not exceed the threshold comprises: determiningwhether the access probability factor is equal to one (1); when theaccess probability factor is not equal to one (1), determining whetherthe number of idle mode mobile stations responding to the controlmessage is equal to zero (0); and when the number of idle mode mobilestations responding to the control message is not equal to zero (0):adjusting the access probability factor based on the number of idle modemobile stations responding to the control message and the threshold toproduce an adjusted access probability factor; determining whether toestablish a PTM communication or a PTP communication based on theadjusted access probability factor.
 8. The method of claim 7, whereinthe control message comprises a first control message, the comparisoncomprises a first comparison and wherein determining, when the number ofidle mode mobile stations responding to the control message is not equalto zero (0), whether to establish a point-to-multipoint (PTM)communication or a point-to-point (PTP) communication based on theadjusted access probability factor comprises: determining whether theadjusted access probability factor is greater than the threshold; whenthe adjusted access probability factor is not greater than thethreshold, determining whether the adjusted access probability factor isgreater than one (1); when the adjusted access probability factor is notgreater than one (1); broadcasting a second control message comprisingthe adjusted access probability factor; receiving, from each of one ormore idle mode mobile stations, a response to the second controlmessage; comparing a number of responses received in response to thesecond control message to the threshold to produce a second comparison;and determining whether to establish a PTM communication or a PTPcommunication based on the second comparison.
 9. The method of claim 7,wherein determining, when the number of idle mode mobile stationsresponding to the control message is not equal to zero (0): whether toestablish a point-to-multipoint (PTM) communication or a point-to-point(PTP) communication based on the adjusted access probability factorcomprises: determining whether the adjusted access probability factor isgreater than the threshold; when the adjusted access probability factoris not greater than the threshold, determining whether the adjustedaccess probability factor is greater than one (1); when the adjustedaccess probability factor is greater than one (1), establishing a PTPcommunication channel with each MS responding to the control message.10. The method of claim 7, wherein the control message comprises a firstcontrol message and the comparison comprises a first comparison, whereindetermining, when the number of idle mode mobile stations responding tothe control message is not equal to zero (0): whether to establish apoint-to-multipoint (PTM) communication or a point-to-point (PTP)communication based on the adjusted access probability factor comprises:determining whether the adjusted access probability factor is greaterthan the threshold; when the adjusted access probability factor isgreater than the threshold, setting the adjusted access probabilityfactor to one (1); broadcasting a second control message comprising theadjusted access probability factor; receiving, from each of one or moreidle mode mobile stations, a response to the second control message;comparing a number of responses, from the one or more idle mode mobilestations to the second control message, to the threshold to produce asecond comparison; and determining whether to establish a PTMcommunication or a PTP communication based on the second comparison. 11.The method of claim 1, wherein determining whether to establish apoint-to-multipoint communication or a point-to-point communicationbased on the number of responses comprises: adjusting the accessprobability factor based on the number of received responses to thecontrol message to produce an adjusted access probability factor;determining whether the adjusted access probability factor is greaterthan or equal to one (1); when the adjusted access probability factor isgreater than or equal to one (1), establishing a point-to-point (PTP)communication channel with each MS responding to the control message.12. The method of claim 11, wherein the control message comprises afirst control message, the comparison comprises a first comparison, andfurther comprising, when the when the adjusted access probability factoris less than one (1): broadcasting a second control message comprisingthe adjusted access probability factor; receiving, from each of one ormore idle mode mobile stations, a response to the second control messagecomprising the adjusted access probability factor; comparing the numberof received responses to the second control message to the threshold toproduce a second comparison; and determining whether to establish apoint-to-multipoint communication or a point-to-point communicationbased on the second comparison.
 13. An apparatus for controlling accessto a Multimedia Broadcast Multicast Service (MBMS) service comprising:at least one memory device that maintains an access probability factorand further maintains a record of a quantity of mobile stations (MSs)subscribed to the MBMS service and maintaining an active connection; aprocessor coupled to the at least one memory device that determines aquantity of mobile stations subscribed to the MBMS service andmaintaining an active connection and an access probability factor byreference to the at least one memory device, conveys a control messagecomprising the access probability factor, receives, from each of one ormore idle mode mobile stations, a response to the control message;compares the number of received responses to a threshold to produce acomparison, and determines whether to establish a point-to-multipointcommunication or a point-to-point communication based on the comparison,determines to establish a point-to-multipoint communication when thenumber of responses exceeds the threshold, upon determining to establisha point-to-multipoint communication, adjusts the access probabilityfactor based on the number of responses from idle mode mobile stationsand the threshold and arranges for conveyance of Multimedia BroadcastMulticast Service data over a point-to-multipoint communication channel.14. The apparatus of claim 13 wherein the threshold comprises athreshold adjusted by the determined quantity of mobile stationssubscribed to the Multimedia Broadcast Multicast Service (MBMS) serviceand maintaining an active connection.
 15. The method apparatus of claim13, wherein, when the number of received responses does not exceed thethreshold, the processor determines whether to establish apoint-to-multipoint (PTM) communication or a point-to-point (PTP)communication based on the access probability factor.
 16. The methodapparatus of claim 15, wherein, when the number of received responsesdoes not exceed the threshold and the access probability factor is notequal to one (1), the processor determining whether to establish apoint-to-multipoint (PTM) communication or a point-to-point (PTP)communication based on the number of idle mode mobile stationsresponding to the control message.
 17. The apparatus of claim 13,wherein the processor determines to convey Multimedia BroadcastMulticast Service (MBMS) data via a point-to-point (PTP) communicationby determining whether the access probability factor is equal to one (1)and, when the access probability factor is equal to one (1), determiningto convey MBMS data via a PTP communication channel.
 18. The apparatusof claim 13, wherein the processor determines to convey MultimediaBroadcast Multicast Service (MBMS) data via a point-to-point (PTP)communication by determining whether the access probability factor isequal to one (1), when the access probability factor is not equal to one(1), determining whether the number of idle mode mobile stationsresponding to the control message is equal to zero (0), and when thenumber of idle mode mobile stations responding to the control message isequal to zero (0), determining to convey MBMS data via a PTPcommunication channel.
 19. The apparatus of claim 13, wherein theprocessor determines whether to establish a point-to-multipoint (PTM)communication or a point-to-point (PTP) communication when the number ofreceived responses does not exceed the threshold by determining whetherthe access probability factor is equal to one (1), when the accessprobability factor is not equal to one (1), determining whether thenumber of idle mode mobile stations responding to the control message isequal to zero (0), and when the number of idle mode mobile stationsresponding to the control message is not equal to zero (0), adjustingthe access probability factor based on the number of idle mode mobilestations responding to the control message and the threshold to producean adjusted access probability factor and determining whether toestablish a PTM communication or a PTP communication based on theadjusted access probability factor.
 20. The apparatus of claim 19,wherein the control message comprises a first control message, thecomparison comprises a first comparison, and wherein, when the number ofidle mode mobile stations responding to the control message is not equalto zero (0), the processor determines whether to establish apoint-to-multipoint (PTM) communication or a point-to-point (PTP)communication based on the adjusted access probability factor bydetermining whether the adjusted access probability factor is greaterthan the threshold, when the adjusted access probability factor is notgreater than the threshold, determining whether the adjusted accessprobability factor is greater than one (1), and when the adjusted accessprobability factor is not greater than one (1), conveying a secondcontrol message comprising the adjusted access probability factor,receiving, from each of one or more idle mode mobile stations, aresponse to the second control message, comparing a number of responsesreceived in response to the second control message to the threshold toproduce a second comparison, and determining whether to establish a PTMcommunication or a PTP communication based on the second comparison. 21.The apparatus of claim 19, wherein, when the number of idle mode mobilestations responding to the control message is not equal to zero (0), theprocessor determines whether to establish a point-to-multipoint (PTM)communication or a point-to-point (PTP) communication based on theadjusted access probability factor by determining whether the adjustedaccess probability factor is greater than the threshold, when theadjusted access probability factor is not greater than the threshold,determining whether the adjusted access probability factor is greaterthan one (1), and when the adjusted access probability factor is greaterthan one (1), arranging to convey Multimedia Broadcast Multicast Service(MBMS) data via a PTP communication channel.
 22. The apparatus of claim19, wherein the control message comprises a first control message, thecomparison comprises a first comparison, and wherein, when the number ofidle mode mobile stations responding to the control message is not equalto zero (0), the processor determines whether to establish apoint-to-multipoint (PTM) communication or a point-to-point (PTP)communication based on the adjusted access probability factor bydetermining whether the adjusted access probability factor is greaterthan the threshold and, when the adjusted access probability factor isgreater than the threshold, setting the adjusted access probabilityfactor to one (1), conveying a second control message comprising theadjusted access probability factor, receiving, from each of one or moreidle mode mobile stations, a response to the second control message,comparing a number of responses to the second control message to athreshold to produce a second comparison, and determining whether toestablish a PTM communication or a PTP communication based on the secondcomparison.
 23. The apparatus of claim 13, wherein the processordetermines whether to establish a point-to-multipoint (PTM)communication or a point-to-point (PTP) communication by adjusting theaccess probability factor based on the number of received responses tothe control message to produce an adjusted access probability factor,determining whether the adjusted access probability factor is greaterthan or equal to one (1), and when the adjusted access probabilityfactor is greater than or equal to one (1), arranging for conveyance ofMultimedia Broadcast Multicast Service (MBMS) data via a PTPcommunication.
 24. The apparatus of claim 23, wherein the controlmessage comprises a first control message, the comparison comprises afirst comparison, and wherein the processor, when the adjusted accessprobability factor is less than one (1), conveys a second controlmessage comprising the adjusted access probability factor, receives,from each of one or more idle mode mobile stations, a response to thesecond control message comprising the adjusted access probabilityfactor, compares the number of received responses to the second controlmessage to the threshold to produce a second comparison; and determineswhether to establish a point-to-multipoint communication or apoint-to-point communication based on the second comparison.